spirv: Add error checking for Block and BufferBlock decorations

Variable pointers being well-defined across the block boundary requires
a couple of very specific SPIR-V validation rules.  Normally, we'd trust
the validator to catch these but since CTS tests have been found in the
wild which violate them, we'll carry our own checks.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/compiler/spirv/spirv_to_nir.c

@@ -563,6 +563,29 @@ struct member_decoration_ctx {
    struct vtn_type *type;
 };
 
+/**
+ * Returns true if the given type contains a struct decorated Block or
+ * BufferBlock
+ */
+static bool
+vtn_type_contains_block(struct vtn_builder *b, struct vtn_type *type)
+{
+   switch (type->base_type) {
+   case vtn_base_type_array:
+      return vtn_type_contains_block(b, type->array_element);
+   case vtn_base_type_struct:
+      if (type->block || type->buffer_block)
+         return true;
+      for (unsigned i = 0; i < type->length; i++) {
+         if (vtn_type_contains_block(b, type->members[i]))
+            return true;
+      }
+      return false;
+   default:
+      return false;
+   }
+}
+
 /** Returns true if two types are "compatible", i.e. you can do an OpLoad,
  * OpStore, or OpCopyMemory between them without breaking anything.
  * Technically, the SPIR-V rules require the exact same type ID but this lets
@@ -1375,6 +1398,17 @@ vtn_handle_type(struct vtn_builder *b, SpvOp opcode,
    }
 
    vtn_foreach_decoration(b, val, type_decoration_cb, NULL);
+
+   if (val->type->base_type == vtn_base_type_struct &&
+       (val->type->block || val->type->buffer_block)) {
+      for (unsigned i = 0; i < val->type->length; i++) {
+         vtn_fail_if(vtn_type_contains_block(b, val->type->members[i]),
+                     "Block and BufferBlock decorations cannot decorate a "
+                     "structure type that is nested at any level inside "
+                     "another structure type decorated with Block or "
+                     "BufferBlock.");
+      }
+   }
 }
 
 static nir_constant *
@@ -3598,6 +3632,7 @@ vtn_handle_preamble_instruction(struct vtn_builder *b, SpvOp opcode,
       case SpvCapabilityVariablePointersStorageBuffer:
       case SpvCapabilityVariablePointers:
          spv_check_supported(variable_pointers, cap);
+         b->variable_pointers = true;
          break;
 
       case SpvCapabilityStorageUniformBufferBlock16:

src/compiler/spirv/vtn_private.h

@@ -586,6 +586,7 @@ struct vtn_builder {
    struct vtn_value *entry_point;
    bool origin_upper_left;
    bool pixel_center_integer;
+   bool variable_pointers;
 
    struct vtn_function *func;
    struct exec_list functions;

src/compiler/spirv/vtn_variables.c

@@ -1686,9 +1686,26 @@ vtn_create_variable(struct vtn_builder *b, struct vtn_value *val,
 
    switch (mode) {
    case vtn_variable_mode_ubo:
+      /* There's no other way to get vtn_variable_mode_ubo */
+      vtn_assert(without_array->block);
       b->shader->info.num_ubos++;
       break;
    case vtn_variable_mode_ssbo:
+      if (storage_class == SpvStorageClassStorageBuffer &&
+          !without_array->block) {
+         if (b->variable_pointers) {
+            vtn_fail("Variables in the StorageBuffer storage class must "
+                     "have a struct type with the Block decoration");
+         } else {
+            /* If variable pointers are not present, it's still malformed
+             * SPIR-V but we can parse it and do the right thing anyway.
+             * Since some of the 8-bit storage tests have bugs in this are,
+             * just make it a warning for now.
+             */
+            vtn_warn("Variables in the StorageBuffer storage class must "
+                     "have a struct type with the Block decoration");
+         }
+      }
       b->shader->info.num_ssbos++;
       break;
    case vtn_variable_mode_uniform: